1. Field of the Invention
The present invention relates to an optical connector for optical communication, in which an optical fiber is adhered and fixed to a ferrule so as to realize coupling.
2. Description of the Related Art
FIG. 3 is a perspective view of an example of a ferrule constituting an optical connector. A ferrule 1 is obtained by forming epoxy-system resin containing silica as filler. In the longitudinal direction of the ferrule 1, a plurality of optical fiber insertion holes 2 are formed, and fitting pin insertion holes 3 are formed in both outsides of the fiber insertion holes 2. In the upper surface, an adhesive injection opening 4 for adhering and fixing optical fibers is formed.
An optical fiber 11 in which the coating of the top layer at an end portion of a multi-coated optical fiber 10 is removed is inserted into the optical fiber insertion hole 2 of the ferrule having such a configuration from a ferrule rear 1a, as shown in FIG. 2. Then a thermosetting epoxy-system adhesive 7 is injected between the ferrule 1 and the optical fiber 11 from the adhesive injection opening 4, and the adhesive is hardened at the temperature of about 80.degree. C. so as to adhere and fix the optical fiber 11. After that, the coupled end surface is ground so as to form an optical connector.
The above-mentioned adhesive used for adhering and fixing an optical fiber needs to have so low viscosity as to be charged quite up to the optical fiber insertion hole, and needs to have so high hardness as to fix the optical fiber firmly not to move at the time of grinding. In addition, with reliability such as chemicals durability and the like taken into consideration, a high-temperature thermosetting epoxy-system adhesive has been used conventionally.
Using a thermosetting epoxy-system adhesive for adhering and fixing an optical fiber and a ferrule, a conventional optical connector has a problem in that the ferrule is tensed so as to be deformed, or the optical fiber is given stress so as to increase the loss in connection of the connector, because of the hardening shrinkage which occurs when the adhesive is hardened at a high temperature, the shrinkage which occurs when the adhesive is cooled down into ordinary temperature after the hardening, and the like.
Although this problem can be solved by using an adhesive which is small in Young's modulus, in linear expansion coefficient, or the like, then there occurs another problem that the force of holding an optical fiber is not enough when the optical fiber on the connector end surface is ground, so that the grinding becomes difficult.